batman-adv: bla: prevent use-after-free when deleting claims

In the Linux kernel, the following vulnerability has been resolved:

batman-adv: bla: prevent use-after-free when deleting claims

When batadv_bla_del_backbone_claims() removes all claims for a backbone, it

does this by dropping the link entry in the hash list. This list entry

itself was one of the references which need to be dropped at the same time

via batadv_claim_put().

But the batadv_claim_put() must not be done before the last access to the

claim object in this function. Otherwise the claim might be freed already

by the batadv_claim_release() function before the list entry was dropped.